<html window-frame="solid"
    window-width="40%"
    window-height="40%" >
    <head>
        <title>Test</title>
        <style>

html { border:3px solid #000; }

        </style>
        <script>

document.on("click", "button#close", function() {
  Window.this.close();
});

        </script>
    </head>

    <header>
      <caption role="window-caption">Window caption</caption>
    </header>

    <body>

<p>window-frame="solid"</p>

<button #close>Close</button> 

    </body>
</html>